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A Progress Report to: 

USDI, Bureau of Land Management 

Lewistown District 

80 Airport Road 

P.O.Box 1160 

Lewistown, Montana 59457 

Submitted by 

Paul Hendricks 

David L. Center 

October 1997 

Montana Natural Heritage Program 

1515 East Sixth Avenue 

Helena, Montana 59620-1800 

© 1997 Montana Natural Heritage Program 

This document should be cited as follows: 

Hendricks, P., and D. L. Center. 1997. Bat surveys of Azure Cave and the Little Rocky Mountains: 1996. Montana 
Natural Heritage Program. Helena, MT. 25 pp. 


Surveys of bat activity at Azure Cave and the surrounding country of the Little Rocky 
Mountains, Phillips County, Montana were conducted during three visits in 1996: 3-5 June, 7-10 
July, 22-24 October. Bats were detected and identified with use of ANABAT ultrasound 
detectors and mists nets. A count of bats in Azure Cave was undertaken during the first visit; 
during the last two visits only surface surveys were conducted. Other sites surveyed included 
stock ponds, forested ravines, a mine adit and a rock-shelter cave. A total of 14 sites in the Little 
Rocky Mountains was surveyed for bat activity during the 1996 inventory. 

Nine species of bats were recorded during 1996: California Myotis (Myotis califomicus). 
Small-footed Myotis (M. ciliolabrum). Long-eared Myotis (M. evotis). Little Brown Myotis (M. 
lucifugus). Long-legged Myotis (M. volans). Big Brown Bat (Eptesicus fuscus). Silver-haired Bat 
(Lasionycteris noctivagans). Hoary Bat (Lasiurus cinereus), Townsend's Big-eared Bat 
(Corynorhinus [=Plecotus] townsendii). All but the Silver-haired Bat were captured at least once 
in mist nets. 

The estimated minimum bat population in Azure Cave on 4 June 1996 was 474; all bats 
noted during the count were Myotis of undetermined species. The species composition and 
population estimate were similar to results from previous surveys made in 1978. Distribution 
within the cave was also similar to previous findings, with >90% of the hibernating bats using the 
Lunchroom. Netting at the mouth of Azure Cave during each visit revealed that several species 
may use the cave for feeding and roosting during summer and fall. Species netted at Azure Cave 
were Cahfomia Myotis, Small-footed Myotis, Little Brown Myotis, Long-legged Myotis, Big 
Brown Bat, and Townsend's Big-eared Bat. Most activity at the mouth of Azure Cave in 
October was by the Big Brown Bat, which has not been noted using the cave as a hibemaculum. 

Ponds appear to be important sources of water and food for bats in the Little Rocky 
Mountains. Five species (12 individuals) were netted during 10 net-hours at "Pond #1," nearest 
Azure Cave, on 9 July. Activity appeared to peak at ponds during the first few hours after sunset, 
with a lesser peak in early morning. Bat activity at sites away from water showed a peak only 
during the first few hours after sunset, except at a mine adit, which may have been used as a day 
roost. Nonetheless, bat activity at water sources was several-fold greater than at sites away from 
water (except Azure Cave and the mine adit) during equivalent time periods, further showing the 
abihty of water sources in the Little Rocky Mountains area to concentrate bat activity following 
evening emergence. 

Mitigation of detrimental impacts on bats in the Azure Cave area should include 
protection of current water sources or the establishment of new sources to replace those lost. 
The probability of protecting Azure Cave as a hibemaculum can be increased by maintaining the 
entrance gate, limiting human access during winter (October-early June), and close monitoring of 
human and bat activity in and near the cave. 



This project was made possible through support of the Montana Natural Heritage 
Program - a collaborative effort of The Nature Conservancy and the Natural Resource 
Information System - and a Challenge Cost Share agreement with the Lewistown District, BLM. 
We especially thank Michelle Williams of the Lewistown District, BLM for support, 
encouragement and assistance in nearly all facets of this project. Sam Martinez, Kathy Jurist, 
Chris Novasio, and Dave Kampwerth all contributed to the collection of field data. We thank the 
"Missouri River Crew", under the guidance of Michelle Williams, for taking time off to help with 
the July sampling. K. Jurist analyzed tapes of bat calls, D. Kampwerth and S. Martinez provided 
invaluable leadership and support in conducting the underground exploration, surveys and 
mapping of Azure Cave. Tom Butts shared his information from a previous visit to Azure Cave. 
Kevin Ryan and his staff at Zortman Mining, Inc. provided logistical support and access to 
abandoned mines in the Zortman area. Joan Gableman, formerly of Zortman Mining, Inc. 
provided valuable information regarding the status and location of abandoned mines in the Little 
Rocky Mountains. 









Azure Cave 5 

Figure 1. Map of Azure Cave showing major hibernation aggregations within the 

cave (Figuresl-Sunavailable) 6 

Table 1. Bats captured with mist nets in the Azure Cave area 8 

Figure 2. Nocturnal bat activity at Azure Cave on two nights 9 

Activity at ponds 10 

Figure 3. Nocturnal bat activity at Pond #1 11 

Figure 4. Nocturnal bat activity at Pond #1 (below Azure Cave) and guzzler 12 

Figure 5. Early-night bat activity over three habitats 13 

Activity patterns away from ponds 14 

Figure 6. Nocturnal bat activity at seven sites 15 

Figure 7. Nocturnal bat activity at three sites on 9 July 16 




Figure 8. Map of locations for bat surveys in the Azure Cave area in 1996 22 


Knowledge of Montana's bat fauna is fragmentary. The most recent summary of bat 
distribution and habitat use in the state (Hoffmann and Pattie 1968, Hoffmann et al. 1969) has 
since been supplemented with the addition of two species new to the state (see Swenson and 
Shanks 1979, Shryer and Flath 1980) and several regional surveys (e.g., Jones et al. 1973, 
Swenson and Bent 1977, Worthington and Ross 1990, Worthington 1991, Roemer 1994, 
Hendricks et al. 1995, 1996). Nevertheless, site surveys have often been brief (lacking the 
thoroughness of an intensive survey), and many areas of Montana remain unsurveyed. Thus, 
much remains to be learned about the distribution, abundance, seasonal movements, and 
reproductive biology of bat species in the state. 

Five species of bats found in Montana (Fringed Myotis, Myotis thysanodes; Northern 
Myotis, Myotis septentrionaUs; Spotted Bat, Euderma maculatum; Townsend's Big-eared Bat, 
Corynorhinus [= Plecotus] townsendn; Pallid Bat, Antrozous pallidus) are on the 1997 Montana 
Natural Heritage Program (MTNHP) "Animal Species of Special Concern" hst, with one 
additional species (Yuma Myotis, Myotis yumanensis) on the informal "Watch List." Four of 
these species were formerly listed by the U.S. Fish and Wildlife Service as Candidates (C2) for 
threatened or endangered status. Three bat species on the MTNHP lists (all but the Myotis 
species) are classified as Sensitive by the U.S. Forest Service or Special Status by the BLM. 
Listed species are of concern for various reasons including rarity, limited distribution, or loss of 
habitat. All listed species, with the exception of the Spotted Bat {Euderma maculatum), use 
caves or mines during some portion of their annual cycle. In Montana, 1 1 (79%) of 14 bat 
species (all but the Spotted Bat, Silver-haired Bat [Lasionycteris noctivagans] and Hoary Bat 
[Lasiurus cinereus]) rely primarily on caves or mines for roost or hibernaculum sites. 

Several species of North American cave-dwelling bats have been adversly affected in 
recent decades by a variety of human-induced environmental changes to caves, including cave 
closures, impoundments, and vandalism or other human disturbances (e.g., Humphrey 1978, 
Tuttle 1979, LaVal and LaVal 1980). These, and landscape changes such as deforestation and 
agricultural development, have forced many bat species to abandon traditional sites in search of 
new roosts and hibemacula. As a result, some cave-dwelling species in the East and Midwest 
have been federally listed as threatened or endangered. Mines offer a variety of subterranean 
microclimates similar to those in natural caves (Tuttle and Stevenson 1978, Tuttle and Taylor 
1994) and can provide suitable habitat for roosting and hibernating bats. In fact, abandoned mines 
now serve as principle roosts and hibemacula for many cave-dwelling species (Tuttle and Taylor 
1994), and are important for populations occupying marginal habitats (Gates et al. 1984) in areas 
where there are continued threats to primary natural roosts. It is widely acknowledged that 
natural cave environments are the most stable and desirable long-term habitats for bats. They 
should be protected and conserved wherever possible to maintain healthy cave-dependent species, 
including bats. 

Mine reclamation (including closure to restrict human access) is of interest to wildlife 
managers because reclamation activities can have significant negative impacts on bat populations 
(e.g., Richter et al. 1993), unless closure is done in such a way as to minimize disturbance to bats 
in the mines affected. Because the majority of bat species in Montana use caves and mines, it is 

especially important to determine the magnitude of mine use by bats in the state and identify 
situations where abandoned mines can be made safe for humans while maintaining their 
attractiveness to bats. 

Azure Cave is located in the Little Rocky Mountains near Zortman, Phillips County, 
Montana. It was named after Pat Azure, who discovered the cave in the late 1950's. Various 
explorations, assessments and collections of the cave and its features were conducted in the early 
1960's (Howard and Hintzman 1964). The cave was immediately recognized as an outstanding 
geological feature in Montana, with exceptional size and extent of its significant speleothems. 
Azure Cave (also known as Zortman Cave) was withdrawn from mineral development in 1963. A 
resource inventory and evaluation by several geologists and biologists was conducted in 1978 
(Chester et al. 1979), representing the first documented bat census in the cave. Numbers and 
distribution of bats encountered at that time indicated Azure Cave to be a significant winter roost 
(hibemaculum), with several hundred individuals present. 

Increased concern over bat populations nationally, and recognition that a good baseline 
inventory was necessary for future local management efforts, convinced BLM managers that a 
thorough assessment of bat activity in Azure Cave and the surrounding area was warranted. The 
Lewistown District, BLM Office contacted the MTNHP in Helena to solicit technical support for 
such a study. This report documents findings from work conducted in 1996, discusses 
observations from previous studies, and offers suggestions for ongoing monitoring in the Little 
Rocky Mountains. Our focus for 1996 was to 1) assess the numbers and significance of bats in 
Azure Cave, and 2) determine the extent of habitat use by bats in the general vicinity of Azure 
cave and identify important habitat attributes in the area. 


Field work on bat activity in and around Azure Cave (Little Rocky Mountains, Phillips 
County, Montana; see Campbell 1978) was conducted during three visits in 1996: 3-5 June, 7-10 
July, 22-24 October. Azure Cave was entered on 4 and 5 June to conduct a thorough pre- 
emergence count of the bat population, gather climatological data, inventory cave formations, 
document evidence of human disturbance, and conduct additional mapping of the cave. Entry in 
early June may have been late for a reliable hibernation count of wintering bats, as events revealed 
many bats were ready for emergence at that time (see Results and Discussion). Care was taken to 
keep disturbance to a minimum during inspection of the cave. Therefore, bats encountered were 
not handled nor marked while we were in the cave. Because of our concern about disturbance, 
and inaccessibility of some hibernating individuals, species identification of all bats in the cave was 
not possible. Counts of all bats encountered were made independently by two observers to 
reduce bias of the total estimate. Location of bats within the cave was recorded to document 
portions of the cave most critical to the bats for hibemacula. 

A preliminary assessment of old mine workings, based primarily on descriptions provided 
by Joan Gableman (formerly with Zortman Mining, Inc.), was conducted to determine their 
suitability as bat habitat. Several adits and shafts were visually inspected, and the Pink-eye Pearl 
Adit #1 was monitored overnight on 9 July. Attempts to visit other caves in the area were 
thwarted by time restrictions, but Two Hands Cave was checked on 9 July and monitored 
overnight for bat activity. 

Bats were captured with mist- nets at the mouth of Azure Cave during each of our visits 
(early June, early July, late October); two nets were used during each period of netting. Mist-net 
surveys were also conducted in July at three of the ponds near Azure Cave; most netting effort 
was focused on "Pond #1" nearest the cave. Number of nets used per site varied from one to six. 
Mist-nets, set singly or in groups, were run for 3-5 hours beginning at dusk; nets were left open 
all night at the mouth of Azure Cave on 22 October. All bats captured were identified, sexed, 
weighed and measured, and marked with colored plastic bands (one band on the forearm, except 
Lasiurus cinereus with two bands). White was used for individuals captured at Azure Cave, 
other colors (light blue for Eptesicus, purple for Myotis, red and another color for Lasiurus) for 
bats captured elsewhere. Bats captured at Azure Cave in June were not color-marked, as bands 
were not yet available. 

Ultrasound detectors were used at 17 different sites, mostly in July, to record overnight 
bat activity. Detectors were used at five sites on more than one night; two sites were monitored 
on more than one field trip. We paid particular attention to bat activity at water sources (stock 
ponds), but also set detectors at sites away from water in forest clearings and near rock outcrops. 
At a few sites (e.g.. Azure Cave, Pond #1) detectors were used in conjunction with mist-nets, to 
obtain a more complete picture of activity by each species. At the time detector units were placed 
we recorded: 1) an index of sky conditions from 0-6 (clear to showers), 2) Beaufort wind scale 
from 0-5 (no wind to winds 19-24 mph), and 3) ambient temperature. 

Thomas and West (1989) provide a general discussion of sampling methods for bats. 
Each method has strengths and weaknesses for survey work, with no single method being 
definitive. Ideally, a combination of mist-nets and bat detectors would be employed at a given site 

in order to obtain the most accurate picture of distribution and relative abundance. Mist-netting 
has the advantage of allowing in-hand identification of individuals and collection of data on sex 
and reproductive condition, neither of which are obtainable with bat detectors. Some bats may 
escape capture in nets, however, and some species present at a particular site may go undetected. 
Also, mist-netting is time-consuming, and therefore permits fewer sites to be surveyed within the 
allotted time period. 

Data collected with bat detectors can supplement or serve in lieu of mist-net data. 
Microchiropteran bats use a variety of ultrasonic vocalizations as echolocation aids for navigation 
and prey capture. Fortuitously, a number of studies have determined that the signals emitted by 
bats can be used to distinguish among many species (e.g., Barclay 1986, Fenton and Bell 1981, 
Fenton et al. 1983, MacDonald et al. 1994). This characteristic permits the assessment of 
species-presence during inventory work through use of portable ultrasound bat detectors. Bat 
detectors are not without drawbacks, however. Call duration, time between calls, call structure, 
and call frequency can vary significantly with habitat and between individuals (Brigham et al. 
1989, Erickson 1993), sometimes making species identification difficult. In the Little Rocky 
Mountains, Myotis evotis was the only species of Myotis which could be distinguished with 
accuracy from other members of the genus using a bat detector. 

ANABAT II bat detectors (Titley Electronics, Ballina, Australia) were used during our 
field work in 1996. These detectors are sensitive to broadband ultrasonic calls common in bat 
vocalizations (usually 20-180 kHz) . Ultrasonic signals in the range of bat vocalizations are 
captured, converted to an audible frequency (up to 10 kHz), and recorded on magnetic tape. 
Detector units (consisting of the detector, timer/tape-driver, and a voice- activated cassette tape 
recorder) were set up before dusk near bodies of water and forest openings (where bat activity 
would be expected) and left in place overnight; usually one cassette tape was sufficient to record 
activity at a single site. Detectors were sensitive to bats within a minimum range of 20-30 m. 
Recorded tapes were returned to the laboratory and analyzed on an IBM compatible PC using an 
ANABAT II ZCA Interface Module and software. Assignment of vocalizations to a particular 
species of bat was achieved by matching field recordings with a reference set of calls obtained 
from captured individuals, in addition to matching call characteristics with those reported in the 

Data collected with the detectors permitted us to perform some analyses of relative bat 
activity between sites and time periods. Activity is defined as the number of passes/hour. With 
these data it is not possible to determine how many individuals were actually present; we assume 
that there is a positive relationship between activity and number of individuals. Statistical 
analyses, where used in this report, follow standard procedures described in Sokal and Rohlf 
(1981), with statistical significance assumed when P < 0.05. 


Azure Cave-A total count of bats in Azure Cave was made on 4 June. Bats were found in three 
locations in the cave (Figure 1): Lunchroom, Music Room, passages beyond the Lunchroom. 
Respective location counts were 421 (88.9%; individual counts of 419 and 423), approx. 35 
(7.4%; individual counts not available), and 18 (3.8%; individual counts of 15 and 20). Thus, 
estimated minimum bat population in the cave at the time of the census was about 474 (range = 
469-478). All bats noted in the cave during the count were Myotis of some species. It is likely 
that other individuals were using the entrance Big Room, but it was impossible to see or verify 
their presence, due to height and surface texture of the room. Over 20 bats were active in and 
around the cave entrance, further indicating the likelihood that some bats were overlooked in the 
Big Room. Typically, most bats in the cave were present as scattered individuals, but clusters of 
up to seven individuals were seen. Fewer than 200 individuals were counted in the same areas on 
5 June, indicating that most bats were emerging from hibernation at the time of the survey. 

The estimated minimum number of individual bats (474) using Azure Cave during our 4 
June 1996 census was remarkably similar to earlier counts of 529 (1 April 1978) and 492 (30 
September 1978) reported by Chester et al. (1979). Location of hibernating bats was also similar 
during the two surveys, with 91.1% of the population in spring 1978, and 95.5% in fall, using the 
Lunchroom (Chester et al. 1979); 88.9% of the population was in the same room in spring 1996. 
Butts (1993) entered Azure Cave on 5 March 1993 and estimated 250-300 bats hibernating in the 
Lunchroom, 94.3-95.2% of his total count, and consistent with other findings of hibernation sites 
within Azure Cave. Because Butts terminated his cave investigation prematurely, however, (due 
to disturbing the bats) his estimate of total bats using the cave is suspect. The best available 
estimates through 1996 suggested that the number of bats using Azure Cave as a hibemaculum 
was relatively stable and in the range of 475-550. A more recent survey (20 April 1997; to be 
discussed in detail in the next progress report) resulted in a count of 1 174-1318 hibernating 
Myotis, indicating that population size of bats using Azure Cave as a hibemaculum may flutuate 
more drastically than previously indicated. Myotis lucifugus and M. volans were identified from 
remains recovered during the April 1997 count. What remains unknown regarding the hibernating 
population in Azure Cave is 1) the species composition of the population, 2) the proportions of 
different bat species using the cave, and 3) the relative annual stability of the total hibernating bat 

There are few published records of winter (1 November- 1 April) bats in Montana. 
Swenson and Shanks (1979) fownd Myotis lucifugus, M. septentrionalis, M. evotis, M. volans, 
and Corynorhinus townsendii hibernating in mines in Richland County near Sidney. Swenson 
(1970) also found M. ciliolabrum and C. townsendii hibemating in coal mines in the Bull 
Mountains of Musselshell County. Other published observations on Montana bats (Hoffmann et 
al. 1969, Jones, et al. 1973, Swenson and Bent 1977) provide no additional records of hibernating 

Figure 1 . Map of Azure Cave showing major hibernation aggregations within the cave. ( u n a va i I a bl e) 

individuals. Additional winter records from the Pacific Northwest of Idaho, Oregon, Washington, 
British Columbia, and Alberta are available for all species identified in the Little Rockies area 
(Schowalter 1980, Center 1986, Perkins et al. 1990, Nagorsen and Brigham 1993, Nagorsen et al. 
1993), indicating the possibility of a diverse winter assemblage of species in and near Azure Cave. 
Hibernating species collected in Azure Cave, and tentatively identified, include Myotis lucifugus, 
M. volans, and Corynorhinus townsendii (Chester et al. 1979, Butts 1993). Certainly, the vast 
majority of bats using Azure Cave as a hibemaculum are species of Myotis. 

Chester et al. (1979) conducted counts of bats in Azure Cave on 9 July and 11 August 
1978, and found zero and four individuals, respectively, indicating the cave is used primarily as a 
hibemaculum. We did not enter the cave during summer, although we did monitor activity at the 
cave entrance during each field trip using mist-nets and bat detectors. Fifteen Myotis lucifugus, 
one M. ciliolabrum, and one M. californicus were captured on 3 June (Table 1) during 6 net- 
hours (2.8 captures/net- hour). On 7 July, one Eptesicus fuscus and one Corynorhinus (= 
Plecotus) townsendii were captured during 9 net-hours (0.2 captures/net- hour). During our final 
field trip to the cave, 10 Eptesicus fuscus, one M. ciliolabrum, and one M. volans were captured 
on 22 October during 24 net- hours (0.5 captures/net-hour; 10 captures occurred during the first 9 
net-hours, for a rate of 1.1 captures/net-hour ), and five E. fuscus were captured on 23 October 
during 8 net-hours (0.6 captures/net- hour). Butts (1993) netted four Myotis lucifugus, one M. 
evotis, five Eptesicus fuscus and one Corynorhinus townsendii at the cave mouth on 28 and 29 
September 1992 (0.4 and 0.7 captures/net-hour, respectively). The pattem of captures is 
consistent with Chester et al.'s (1979) finding of greatly reduced use of the cave during summer. 
Bats captured by us in June were both entering and leaving the cave, the two bats captured in July 
were entering the cave, and about equal numbers were caught entering and leaving the cave in 
October. Our bat detector data showed Corynorhinus townsendii present during the June sample 
and Myotis evotis present in July. Thus, at least seven species of bats use Azure Cave as a 
hibemaculum, a feeding site, and/or a roost. 

Pattems of evening activity at the cave entrance varied significantly (G = 88.424, df = 4, P 
« 0.001) between the 3 June and 7 July samples (Figure 2). Activity in June was late relative to 
dusk, with peak activity beginning about midnight (ca. 3 hours after dusk). In contrast, bats 
became most active within the first hour after dusk on 7 July. Peak activity in July (55 passes in 
an hour) was nearly three-fold that in June (20 passes in an hour), which is probably related to the 
June bats just beginning to emerge from hibemation. Myotis sp. was identified on 83% of the 3 
June passes, 75% of the 7 July passes. Corynorhinus (= Plecotus) townsendii was detected on 
15% and 9% of the passes, respectively, with most (93%) Corynorhinus activity on both dates 
occurring between midnight and 02:00. C. townsendii typically emerge from their roosts at dusk 
in the deserts of Oregon in May, and forage nearby for the first few hours before moving to more 
distant locations to feed (Dobkin et al. 1995). This pattem of activity, if applicable to populations 
in the Little Rockies, would indicate that most C. townsendii detected at Azure Cave during July 
were roosting at other sites. 

Table 1. Bats captured with mist nets in the Azure Cave area (Little Rocky Mountains), Phillips 
County, Montana in 1996. 




Number and Sex 

California Myotis 

(Myotis californicus) 

Azure Cave 

3 Jun 


Western Small-footed 


(M. ciliolabrum) 

Azure Cave 

3 Jun 
22 Oct 


Pond #1 

9 Jul 


Western Long-eared Myotis 

(M. evotis) 

Pond #1 

9 Jul 


Little Brown Myotis 

(M. lucifugus) 

Azure Cave 

3 Jun 

12M 3F 

Pond #1 

9 Jul 


Long-legged Myotis 

(M. volans) 

Azure Cave 

22 Oct 


Big Brown Bat 

(Eptesicus fuscus) 

Azure Cave 

7 Jul 

22 Oct 

23 Oct 

9M IF 


Pond #1 

8 Jul 

9 Jul 


Pond #2 

8 Jul 


Hoary Bat 
(Lasiurus cinereus) 

Pond #1 

9 Jul 

2M 2F 

Townsend's Big-eared Bat 
(Corynorhinus towns endii) 

Azure Cave 

7 Jul 


see Appendix 1 for legal descriptions of locations. 

Figure 2. Nocturnal bat activity at Azure Cave on two nights, based on ANABAT detector data: 
open bars - 3 June, shaded bars - 7 July. ( u n a va i I a bl e) 

Activity at ponds-Bats were detected at five (83.3%) of six ponds monitored in July (see 
Appendix 1 for locations). Mean number (±SD) of passes/hour during peak activity at the five 
ponds was 89.4+25.6. In four of five cases the peak occurred between 22:00-23:00; at the fifth 
pond the peak occurred from 03:00-04:00 (this pond, too, showed elevated activity between 
22:00-23:00). The difference in peak activity between ponds may be a sampling artifact (see 
below). Only the pond with the early-morning peak had an all-night record of activity. Detectors 
ran out of tapes by midnight at the other ponds. 

Activity was monitored most intensively at Pond #1 (the pond nearest Azure Cave). On 
two consecutive nights, bat activity reached a peak between 22:00-23:00 and remained high until 
midnight (Figure 3), when tapes ran out. Although peak activity was about 33% greater on the 
second night (8 July), the pattern of activity until midnight was nearly identical on both nights (G 
= 1.064, df = 2, P > 0.5). Thus, the use of this pond by bats, and the pattern of activity displayed, 
was not an isolated event;. Pond #1 probably attracted considerable bat activity throughout the 
summer, although this is not known with certainty. 

The significance of ponds for the bats can be illustrated by comparing activity on 7 July at 
Pond #1 and a stock tank (full of water) with guzzler located about 50 m downstream from the 
pond. The pattern of bat activity at both sites was similar (G = 0.272, df = 2, P > 0.5), with peaks 
reached at 22:00-23:00 (Figure 4) and maintained to midnight, at least. Peak activity was ten-fold 
greater at Pond #1, however, than at the nearby guzzler and stock tank. This indicates a relatively 
large magnitude of bat activity tightly concentrated over the pond, even though water was also 
present (but in a much smaller amount) only 50 m distant. 

Activity at the guzzler peaked again from 02:00-03:00 (9 passes). Given the similar 
distributions of activity at Pond #1 and the guzzler earlier in the night (Figure 4), 98 passes would 
have occurred over the pond from 02:00-03:00 (calculated from ratios between the two sites for 
the 22:00-23:00 period). This suggests that the all-night pattern of bat activity at ponds discussed 
earlier (early evening and early morning peaks at one pond sampled all night) was probably the 
norm in July at most ponds in the immediate area of Azure Cave. Bimodal patterns of nocturnal 
activity are typical elsewhere for many of the bat species found in Montana (van Zyll de Jong 
1985, Nagorsen and Brigham 1993), including those detected in the Azure Cave area. 

Data are available for comparing bat activity between 21:00-24:00 (during 7-9 July) at 
ponds versus caves/adits and forested sites away from water bodies. Mean activity was greatest 
near caves/adits (mean = 16.5 passes/hour, n = 3 sites) during the first hour after dusk (Figure 5). 
The pattern changes dramatically from 22:00-24:00, when mean activity at ponds (n = 4 sites) is 
three- to five-fold greater than at caves/adits, and nine- to eleven-fold greater than in dry forested 
areas (n = 6 sites). Again, it is clear that bats are concentrating their foraging activity at ponds. 
Ponds are important for bats as sources of drinking water and places to hunt concentrations of 
insect prey (e.g., Brian et al. 1995, Krusic et al. 1996); distance to water may also be a limiting 
factor for nursery colony location (Tuttle and Taylor 1994). 

At least six species of bats foraged over Pond #1 during 7-9 July. Myotis ciliolabrum (1), 
M. lucifugus (1), M evotis (1), Eptesicus fuscus (5), and Lasiurus cinereus (4) were captured 
on 9 July during 10 net-hours of trapping (Table 1); E. fuscus (2) was netted during 4 net-hours 
the previous night. Two of four Lasiurus cinereus were lactating females, all other individuals 
were non-scrotal males. Because we marked all captured bats, and none were recaptured, it is 


Figure 3. Nocturnal bat activity at Pond #1 (below Azure Cave) on two consecutive nights, based 
on ANABAT detector data: open bars - 7 July, shaded bars - 8 July. ( u n a va i I a bl e) 


Figure 4. Nocturnal bat activity at Pond #1 (below Azure Cave) and guzzler on 7 July, based on 
ANABAT detector data; guzzler (with stock tank) was located 50 m downstream from the pond. 
Open bars - pond, shaded bars - guzzler. ( u n a va i I a bl e) 


Figure 5. Early-night bat activity over three habitats in the Azure Cave area during 7-9 July. 
Squares are ponds (4 samples), circles are caves/adits (3 samples), triangles are forested ravines 
(6 samples). ( u n a va i I a bl e) 


highly probable that 14 individuals using the pond is an under-estimate (probably large) of actual 
activity during our trapping. Corynorhinus (= Plecotus) townsendii, though not captured, was 
detected over the ponds 7-8 July and likely was present on 9 July. This further indicates that 
several bats active at Pond #1 were not captured during our trapping sessions. 

Activity patterns away from ponds-Nocturnal activity by bats away from ponds was also 
bimodal. All-night bat detector data collected during 7-9 July from seven sites other than ponds 
and Azure Cave show a broad peak (mean = 6.5-8.7 passes/hour) for the first three hours after 
dusk, with a second moderate peak (mean = 3.8-4.1 passes/hour) between 02:00-04:00 (Figure 
6). This corresponds roughly to the bimodal pattern detected at water sources, but the activity 
level was much weaker. Most of the pattern is driven by Myotis sp. and Eptesicus fuscus; 94.8% 
of the detections were these two "species." Three species (Myotis, E. fuscus, and Corynorhinus 
townsendu) showed two major activity periods. Myotis and Corynorhinus peaked at 22:00-24:00 
and again at 02:00-04:00; Eptesicus was most active slightly earlier, at 21:00-23:00 and again at 

Nocturnal activity at sites away from water was not uniform among sites during any single 
night. Two Hands Cave (a rock shelter with about 30 m of passage). Azure Cave Road #1 (at the 
beginning of the trail head to Azure Cave) and the Pink-eye Pearl Adit were monitored with bat 
detectors all night on 9 July. Activity at Two Hands Cave and Azure Cave Road #1 showed peak 
activity at 21:00-22:00 and again at 23:00-24:00, while activity was relatively constant at the 
Pink-eye Pearl Adit until a peak at 02:00-04:00 (Figure 7); the activity patterns differed 
significantly among the three sites (G = 127.08, df = 14, P « 0.001). Perhaps the mine adit was 
a day roost and a foraging site, while the other two sites were foraging areas only, used mostly by 
bats recently emerged from day roosts. 

Peak activity was similar in magnitude among sites (27 passes/hour at Two Hands Cave, 
20 passes/hour at Azure Cave Road #1,21 passes/hour at the Pink-eye Pearl Adit), but the 
proportions of activity attributable to various bat species differed significantly among sites (G = 
22.154, df = 4, P < 0.001). Percentage of total passes attributable to Myotis was 60.0, 89.8, and 
71.4 for Two Hands Cave, Azure Cave Road #1, and Pink-eye Pearl Adit, respectively; 
percentage for Eptesicus was 38.3, 5.1, and 23.8, respectively, with the remaining (1.7%, 5.1%, 
and 4.8%, respectively) attributable to Lasionycteris noctivagans at the first two sites, and 
Corynorhinus townsendii at the mine adit. 

The above analyses show that different bat species use areas away from ponds unevenly 
over relatively small landscapes on the same night. This may complicate management activities 
intended to enhance bats or bat habitat away from water sources, and could necessitate species- 
specific management rather than a broad plan to cover all bat species. 


Figure 6. Nocturnal bat activity at seven sites (other than ponds or Azure Cave) in the Azure 
Cave area, 7-9 July, based on ANABAT detector data. Species codes are MYSP - Myotis sp., 
EPFU - Eptesicus fuscus, COTO - Corynorhinus townsendii, LACI - Lasiurus cinereus, LANO 
Lasionycteris noctivagans. ( u n a va i I a bl e) 


Figure 7. Nocturnal bat activity at three sites on 9 July. Open bars - Two Hands Cave, black bars 
- Azure Cave Road #1 (a forested ravine), shaded bars - Pink-eye Pearl adit. ( u n a va i I a bl e) 



The following recommendations are presented with the understanding that events in the 
future may dictate actions not identified during this and previous surveys as addressing immediate 
needs to maintain viable populations of bats in and around Azure Cave. In some cases, 
recommended action may already have been taken; such recommendations are included here to 
emphasize their continued applicability to the Azure Cave area. 

1) The gate on Azure Cave does not quite follow recommended construction specifications 
(Tuttle and Taylor 1994) of minimum horizontal distance between vertical supports of two feet, 
with greater distance preferred. Vertical distance between horzontal spacings are variable but 
near the recommended range of 5 3/4 inches to 6 inches. Several species of bats obviously use 
the cave with the present gate in place, but some individuals may be inhibited from entering the 
cave. Furthermore, the design of the current gate is not as secure from human intrusion as that 
recommended in Tuttle and Taylor (1994). Replacement of the gate with a recommended design 
should be considered as a future management activity. 

2) Change the lock on the cave gate every year or two to reduce the likelihood of unsupervised 

3) Maintain a logbook of visitors at the District Office and the cave entrance. This will provide a 
record of activity at the cave, upon which future changes in admission policy can be based, and 
identifies individuals and groups that may be solicited for assistance in future management 
activities involving the cave. 

4) Conduct annual counts of hibernating bats in Azure Cave for 2-3 years, then conduct counts 
once every 2-3 years. 

5) Access to Azure Cave during winter (October-late May) should be permitted only in 
exceptional circumstances, to minimize disturbance to hibernating bats. Groups entering the cave 
during winter should be knowledgable about the need to keep disturbance of bats to a minimum. 

6) Monitor bat activity at nearby ponds. Water sources in the area are extremely significant to the 
bat fauna as sites for feeding and drinking, and also serve as important habitat for amphibians. 
Three amphibian species. Northern Leopard Frog (Rana pipiens). Western Chorus Frog 
(Pseudacris triseriata) and Tiger Salamander (Ambystoma tigrinum), were noted using the ponds 
in the Azure Cave area during 1996. New ponds should be constructed closer to the cave in 
appropriate sites that will retain water if current ponds are to be removed or filled. 

7) Continue surveys of abandoned mines and caves in the area for bat activity and use. The 
information gained will provide a more complete picture of the significance of Azure Cave to the 
bat fauna of the Little Rocky Mountains. 



Barclay, R. M. R. 1986. The echolocation calls of Hoary (Lasiurus cinereus) and Silver-haired 

(Lasionycteris noctivagans) bats as adaptations for long- versus short-range foraging 

strategies and the consequences for prey selection. Can. J. Zool. 64:2700-2705. 
Brigham, R. M., J. E. Cebek, and M. B. C. Hickey. 1989. Intraspecific variation in the 

echolocation calls of two species of insectivorous bats. J. Mamm. 70:426-428. 
Butts, T. W. 1993. Azure Cave bat surveys. Little Rocky Mountains, Montana: September 

1992 and March 1993. Westech, unpub. report. 13 pp. 
Campbell, N.R 1978. Caves of Montana. Mont. Bur. Mines Geol. Bull. 105. 169 pp. 
Chester, J. M., N. P. Campbell, K. Karsmizki, and D. Wirtz. 1979. Resource inventory and 

evaluation. Azure Cave, Montana. B.L.M. unpub. report. 55 pp. 
Dobkin, D. S., R. D. Gettinger, and M. G. Gerdes. 1995. Springtime movements, roost use, and 

foraging activity of Townsend's Big-eared Bat (Plecotus townsendii) in central Oregon. 

Great Basin Nat. 55:315-321. 
Erickson, J. L. 1993. Bat activity in managed forests of the southwestern Cascade Range. 

Master's Thesis, Univ. Washington. 66 pp. 
Fenton, M. B., and G. P. Bell. 1981. Recognition of species of insectivorous bats by their 

echolocation calls. J. Mamm. 62:233-243. 
Fenton, M. B., H. G. Merriam, and G. L. Holroyd. 1983. Bats of Kootenay, Glacier, and Mount 

Revelstoke national parks in Canada: identification by echolocation calls, distribution, and 

biology. Can. J. Zool. 61:2503-2508. 
Gates, J. E., G. A. Feldhamer, L. A. Griffith, and R. L. Raesly. 1984. Status of cave-dwelling 

bats in Maryland: importance of marginal habitats. Wildl. Soc. Bull. 12:162-169. 
Center, D. L. 1986. Wintering bats of the Upper Snake River Plain: occurrence in lava-tube 

caves. Great Basin Nat. 46:241-244. 
Hendricks, P., K. Jurist, D. L. Center, and J. D. Reichel. 1995. Bat survey of the Sioux District, 

Custer National Forest: 1994. Montana Natural Heritage Program. Helena, MT. 41 pp. 
Hendricks, P., K. A. Jurist, D. L. Center, and J. D. Reichel. 1996. Bats of the Kootenai National 

Forest, Montana. Montana Natural Heritage Program. Helena, MT. 99 pp. 
Hickey, M. B. C, and A. L. Neilson. 1995. Relative activity and occurrence of bats in 

southwestern Ontario as determined by monitoring with bat detectors. Can. Field-Nat. 

Hoffmann, R. S., and D. L. Pattie. 1968. A guide to Montana mammals. Univ. of Montana, 

Missoula, MT. 133 pp. 
Hoffmann, R. S., D. L. Pattie, and J. F. Bell. 1969. The distribution of some mammals in 

Montana. II. Bats. J. Mamm. 50:737-741. 
Howard, P. E., and D. Hintzman. 1964. Zortman Cave survey project. Unpublished U.S. Forest 

Service Memo 2300 (2800), Lewis and Clark National Forest. 8 pp. 
Humphrey, S. R. 1978. Status, winter habitat, and management of the endangered Indiana bat, 

Myotis sodalis . Fla. Sci. 41:65-76. 


Jones, J. K., Jr., R. P. Lampe, C. A. Spenrath, and T. H. Kunz. 1973. Notes on the distribution 

and natural history of bats in southeastern Montana. Occ. Pap. Mus. Texas Tech. Univ. 

No. 15. 12 pp. 
Krusic, R. A., M. Yamasaki, C. D. Neefus, and P. J. Pekins. 1996. Bat habitat use in White 

Mountain National Forest. J. Wildl. Manage. 60:625-631. 
LaVal, R. K., and M. L. LaVal. 1980. Ecological studies and management of Missouri bats, with 

emphasis on cave-dwelling species. Missouri Department of Conservation Terrestrial 

Series #8. 53 pp. 
McDonald, K. E., E. Matsui, R. Stevens, and M. B. Fenton. 1994. Echolocation calls and field 

identification of the Eastern Pipistrelle {Pipistrellus subflavus: Chiroptera: 

Vespertilionidae), using ultrasonic bat detectors. J. Mamm. 75:462-465. 
Nagorsen, D. W., and R. M. Brigham. 1993. The bats of British Columbia. Univ. British 

Columbia Press, Vancouver. 164 pp. 
Nagorsen, D. W., A. A. Bryant, D. Kerridge, G. Roberts, A. Roberts, and M. J. Sarell. 1993. 

Winter bat records for British Columbia. Northwest. Nat. 74:61-66. 
Perkins, J. M., J. M. Barss, and J. Peterson. 1990. Winter records of bats in Oregon and 

Washington. Northwest. Nat. 71:59-62. 
Richter, A. R., S. R. Humphrey, J. B. Cope, and V. Brack, Jr. 1993. Modified cave entrances: 

thermal effect on body mass and resulting decline of endangered Indiana bats (Myotis 

sodalis). Cons. Biol. 7:407-415. 
Roemer, D. M. 1994. Results of field surveys for bats on the Kootenai National Forest and Lolo 

National Forest of western Montana, 1993. Montana Natural Heritage Program. Helena, 

MT. 19 pp. 
Schowalter, D. B. 1980. Swarming, reproduction, and early hibernation of Myotis lucifugus and 

M. volans in Alberta, Canada. J. Mamm. 61:350-354. 
Schyrer, J., and D. Flath. 1980. First record of the Pallid Bat (Antrozous pallidus) from 

Montana. Great Basin Nat. 40: 1 15. 
Sokal, R. R., and F. J. Rohlf. 1981. Biometry, second edition. W. H. Freeman, San Francisco. 

859 pp. 
Swenson, J. E. 1970. Notes on distribution of Myori^ /e/Z?// in eastern Montana. Blue Jay 

Swenson, J. E., and J. C. Bent. 1977. The bats of Yellowstone County, southcentral Montana. 

Proc. Mont. Acad. Sci. 37:82-84. 
Swenson, J. E., and G. F. Shanks, Jr. 1979. Noteworthy records of bats from northeastern 

Montana. J. Mamm. 60:650-652. 
Thomas, D. W., and S. D. West. 1989. Sampling methods for bats. Gen. Tech. Rep. PNW- 

GTR-243. Portland, OG: U.S. Dept. Agri., Forest Serv., Pacific Northwest Research 

Station. 20 pp. (Ruggiero, L. F., and A. B. Carey, tech. eds.; Wildlife-habitat 

relationships: sampling procedures for Pacific Northwest vertebrates). 
Tuttle, M. D. 1979. Status, causes of decline, and management of endangered gray bats. J. 

Wildl. Manage. 43:1-17. 
Tuttle, M. D., and D. E. Stevenson. 1978. Variation in the cave environment and its biological 

implications. Pp. 108-121 in 1977 National Cave Management Symposium Proceedings 


(R. Zuber, J. Chester, S. Gilbert, and D. Rhodes, eds.). Adobe Press, Albuquerque, NM. 

140 pp. 
Tuttle, M. D., and D. A. R. Taylor. 1994. Bats and mines. Bat Cons. International Resource 

Pub. No. 3. 41 pp. 
van Zyll de Jong, C. G. 1985. Handbook of Canadian mammals. 2. Bats. Nat. Mus. Nat. Sci. 

Ottawa, Canada.212 pp. 




Figure 8. Map of locations for bat surveys in the Azure Cave area in 1996. ( u n a va i I a bl e) 


Appendix 1. Survey sites for bats in the Little Rocky Mountains, Phillips County, Montana 
during 1996, and bat species detected. 



Bat species" 

Azure Cave 

(T25N R25E S29NW) 

3 June 


7 July 


22 October 




Azure Cave Road #1 
(T25N R25E S20SW) 

23 October 
9 July 





22 October 


Azure Cave Road #2 
(T25N R25E S20SW) 

Azure Cave Road #3 
(T25N R25E S20SE) 

9 July 
9 July 




Pond #1, below Azure Cave 

7 July 





Appendix 1 (cont.). Survey sites for bats in the Little Rocky Mountains, Phillips County, 
Montana during 1996, and bat species detected. 



Bat species" 

Pond #1, below Azure Cave (cont.) 

7 July (guzzler) 





8 July 


9 July 






Pond #2, below Azure Cave 

7 July 




Pond #3, below Azure Cave 

(T25N R25E S33NE) 

8 July 
8 July 

23 October 

Pond #4, below Azure Cave 

7 July 

(T25N R25E S33SW) 

Pond #4 Cottonwood grove 

7 July 

(T25N R25E S33SW) 

8 July 



No calls 

No calls 

No calls 



Appendix 1 (cont.). Survey sites for bats in the Little Rocky Mountains, Phillips County, 
Montana during 1996, and bat species detected. 

Location Date Bat species" 

Highway Pond 8 July MYSP 

(T25N R25E S34SE) EPFU 


Pink Eye Pearl Adit #1 9 July MYSP 

(T25N R25E S7/ T25N R24E S 1 2) EPFU 


Two Hands Cave 9 July MYSP 

(T25N R25E S30SE) LANO 


Dry Gulch, Canyon Mouth 8 July MYSP 

(T25N R24E S35NW) EPFU 


Dry Gulch Pond 8 July MYSP 

(T25N R25E S7NW) EPFU 


' MYSP-Afyoto sp., MYCA-Myotis californicus (Cahfornia Myotis), MYCl-Myotis ciliolabrum 
(Western Small-footed Myotis), MYEN-Myotis evotis (Western Long-eared Myotis), MYLU- 
Myotis lucifugus (Little Brown Myotis), MYWO-Myotis volans (Long-legged Myotis), EPFU- 
Eptesicus fuscus (Big Brown Bat), l^lKi^O-Lasionycteris noctivagans (Silver-haired Bat), LACI- 
Lasiurus cinereus (Hoary Bat), COTO-Corynorhinus (= Plecotus) townsendii (Townsend's Big- 
eared Bat).